Yields vary from a few tons to 25 tons an acre; even larger yields have been secured from small areas of high fertility. With approved methods it should not be less than 15 tons an acre. A Colorado grower in 1908 averaged 25 tons an acre on a 12-acre field and the net returns were $340 an acre. This, however, is much beyond the returns of most growers. The eleventh census report states that the net profit an acre of the 77,000 acres grown in the United States is $118. The large proportion of early cabbage grown in the South is doubtless responsible to a great extent for this good showing. It is generally conceded that early cabbage is more profitable than late. Northern growers often clear $200 an acre. Prices for the late crop are extremely variable. When sold out of the field the price ranges from $2 to $15, and out of storage from $8 to $60; when sold by the head, the price runs from $2 to $6 a hundred, and 60 cents to $3 a crate or a barrel.
Chicago Wholesale Cabbage Prices*
The usual estimates for the cost of producing and marketing an acre of cabbage are too low; $125 an acre for early cabbage and at least one-third this amount for late are not too high. Large net returns are seldom secured without a liberal outlay. With favorable markets or good shipping facilities it is unquestionably one of our most profitable vegetables.
The Cabbage Maggot (Pegomya Brassicae) was introduced from Europe early in the nineteenth century. It feeds upon various cruciferous plants, but is espedaily troublesome to cabbage and cauliflower. Chittenden ("Insects Injurious to Vegetables," p. 132) claims that the insect has been on the increase since 1902.
* American Agriculturist.
The adult resembles the common house fly, but is considerably smaller. It begins laying eggs early in spring, depositing them on or near the stems of the young plants. Slingerland observed that the fly makes its first appearance on Long Island the latter part of April, and that larvae were first seen in early May. From 4 to 10 days are required for hatching. The larva or maggot is footless, shining white, sometimes tinged with yellow and when full grown is 0.32 of an inch long. It prefers feeding on the young tender rootlets, but also erodes and girdles the stem of the plant, often boring into the lower part of the root. It pupates within its own hardened skin in soil about infested plants. The time required for pupation is from 15 days to 3« months. A second brood emerges about the middle of June and changes to puparia in July. The life history from this time is unknown, but it is thought that the insects pass the winter as maggot, pupa and fly.
Numerous remedies are recommended, but one of the best is to place card disks about the plants before egg laying begins. (Cornell Station Bulletin 78, pp. 481-574). Although effective, the making and placing of these cards is tedious and the plan is not generally popular with extensive growers. Carbolic acid emulsion (133) is the most practical means of controlling the pest. It should be diluted about 30 times and applied by spraying on the stems of the plants before egg-laying begins, and repeated if necessary. Experiments made at Geneva, N. Y. (New York Station Bulletin 301), show that growing the plants in frames covered with cheesecloth is a satisfactory method of protection before transplanting.
The Cabbage Aphis (Aphis Brassicae), also known as the cabbage louse, has been known in America for over a century, and has become disseminated throughout the country. Its destructiveness varies greatly from year to year, depending upon seasonal conditions and the prevalence of natural enemies. In many states it was especially troublesome and caused heavy losses in 1908 and 1909. Both seasons were drier than usual, and it seemed that neither insect nor fungous foes had much effect in checking the ravages of the aphis. Protracted drouth unquestionably favors the multiplication of this pest, while low temperatures with heavy rainfalls are the most unfavorable conditions.
This insect usually appears in the North the latter part of May or early in June, and feeds upon both upper and under sides of the leaves, which they cause to curl. The pest multiplies with marvelous rapidity, producing from a dozen to a score of broods in a season. (Bulletin 2, Virginia Truck Experiment Station, Norfolk, Va.) The bodies of the mature forms are green, but are covered with a grayish, powdery coating, which at a distance gives the appearance of mildew. The young are ready to reproduce in five or six days.
The eggs, which pass the winter attached to the stems and the refuse leaves, give rise to the first broods next spring. This suggests the most effective means of prevention: all refuse in infested fields should be destroyed in the fall. It is also important to destroy remnants of infested plants from which the summer crop has been harvested.
Spraying with kerosene emulsion, diluted to 15 parts, is a satisfactory means of controlling the insect on growing plants. The first application should be made before the infestation becomes general. A knapsack sprayer, with the proper nozzle and extension attachments may be used to advantage in spraying isolated plants and small plantations. It is important that the material be applied to the underside of the leaves as well as to the upper surfaces. To accomplish this thoroughly seems almost impossible with a power machine.